The Japanese honeybees forming a "bee ball" around 2 hornets. Photo by Takahashi, Wikimedia Commons

Japanese honeybees (Apis cerrana japonica), over eons of cohabitation, have evolved a unique defensive behavior to combat Japanese giant hornets (Vespa mandarinia). Japanese giant hornets feed their larvae with protein garnered from the larvae or carcasses of other insects, and often attack honeybee hives to obtain honeybee larvae. The hornets are formidable killers, using their sharp talons and powerful mandibles to sever limbs and heads. European honeybees (Apis mellifera) have no answer for these predators, and European honeybee hives are quickly decimated by the hornets, which chew the honeybee larvae into a protein paste to give to young hornet larvae.

The Japanese honeybees have a distinct defensive behavior in response to hornet predation. If a hornet scout enters the hive, the bees will “ball” the hornet by swarming it. The effect of the swarming is to raise the temperature of the “ball” interior to 117ºF, a temperature lethal to the hornet, but not to the bees. The hornet is killed from overexposure to heat, and the hive is saved.